As is generally well known in the railway industry, truck mounted braking systems comprise, in addition to a pair of brake beams, a series of force transmitting members such as levers and linkages, which function to move a group of brake shoes against the wheels of a railway vehicle to effect stoppage of such railway vehicle.
The force-transmitting levers are pivotally connected to each brake beam at its midpoint and utilize lever arms for connection to the force-transmitting members. One of the force-transmitting members is a slack adjuster device, the other force-transmitting member includes a pneumatically actuated brake cylinder device, the body of which is mounted on a first brake beam between the beam tension and compression members adjacent the strut bar, and a connecting rod disposed intermediate the transfer lever arm of a second brake beam and the cylinder body.
The brake cylinder piston push rod is connected to the transfer lever arm of the first brake beam. The cylinder initiates movement of this series of force transmitting members, levers and linkages to apply the brakes of the railway vehicle mounted to a truck assembly of the railway vehicle. A well known type of truck mounted braking systems is a TMX.RTM. truck mounted braking system (TMX.RTM. is a registered trademark of Westinghouse Airbrake Company, the assignee of the present invention).
The TMX was designed for the standard North American three-piece railway truck application. In this brake application, TMX simultaneously exerts an outward brake shoe force to an exterior wheel surface of each wheel disposed within a railway truck. Applications where brake shoe force is high can cause an unwanted movement in the wheel axle area of the truck.
U.S. Pat. No. 3,148,749 teaches a well-known type of disk brake assembly comprising a pair of pivoted brake-shoe-carrying levers or tongs that are actuated by movement of a wedge member between rollers mounted on the outer ends of the levers to thereby rock these levers until the brake shoes are forced into frictional engagement with the opposite sides of a rotor. Furthermore, U.S. Pat. No. 4,337,690 teaches a BFC brake system utilizing a fluid pressure actuated cylinder employing wedges attached to a piston which transmits force to the brake shoe upon pressurization of such cylinder.
The teachings of U.S. Pat. No. 3,148,749 and U.S. Pat. No. 4,337,690 are incorporated herein by reference thereto.
The application of these types of disk brake systems requires installation thereof at each wheel of the railway truck thereby significantly increasing overall brake system costs.
As it can be seen from the above discussion it is desirable to improve TMX.RTM braking system performance to eliminate this unwanted movement and provide a more economical alternative to a standard disk thread brake unit.